Turbodrill

ABSTRACT

A turbodrill comprises a housing coupled with its one end to a drill pipe for feeding drilling fluid, the housing accommodating a hydraulic downhole motor comprising a multistage turbine. Each stage of the multistage turbine comprises a directing stator disk defining through passages and a working rotor disk defining through passages, the rotor disk being installed on a shaft. The shaft is rotatably mounted in the housing on supports and carries a rock breaking tool on the end thereof facing the bottomhole. The total area of the inlet openings of the stator disk through passages is from about ⅕ to about ⅗ of the total area of the inlet openings of the rotor disk through passages.

FIELD OF THE INVENTION

[0001] The present invention relates to the drilling technology fordrilling wells in different geologic rocks, and more particularly to aturbodrill.

BACKGROUND OF THE INVENTION

[0002] Increasing volumes of drilling production and prospecting wellsfor oil and gas recovery have called for the development of new typeturbodrills allowing the use of present-day rock breaking tools madefrom high-strength hard-alloy materials with a torque strength on theshaft of the order of 2000 Nm. However, the known designs of hydraulicdownhole motors used in turbodrills cannot provide normal operation ofthe new type rock breaking tools because of the low power and torquestrength.

[0003] Therefore, attempts to increase the torque strength of thedownhole motor transmitted to the turbodrill rock breaking tool have ledto the development of a turbodrill described in the “Drilling Engineer'sHandbook” by V. I. Mishchevich and N. A. Sidorov (Eds.), vol. 1, Moscow,Nedra Publ. House, pp. 212-213, FIG. VI.1, 1973 (in Russian). The knownturbodrill comprises a housing coupled with its one end to a drill pipefor feeding drilling fluid. The housing accommodates a hydraulic motorcomprising a multistage turbine, each stage of which is constituted by adirecting stator disk defining through passages and a working rotor diskdefining through passages. The rotor disk is installed on a shaftrotatably mounted in the housing on supports and carries a rock breakingtool on the end thereof facing the bottomhole. The total sectional areaof the stator disk through passages corresponds to the total sectionalarea of the rotor disk through passages.

[0004] The through passages of the stator and rotor disks are defined byprofiled blades providing an increase of the drilling fluid pressure,that results in an increase of the power and torque strength acting onthe rock breaking tool. In order to substantially increase the downholedrive power and the developed torque strength on the rock breaking tool,more than 300 stages are installed on the shaft thereof, the resultbeing a significant increase of the turbodrill dimensions, causingdeformation of the stator and rotor disks, that may lead to breakagethereof. As a result, the turbodrill service life becomes reduced, andthe cost of drilling operations increases. The closest technicalsolution in terms of the totality of essential features and of theachieved result is a turbodrill known from the textbook “Drilling Oiland Gas Wells” by Sereda N. G., Soloviev E. M. (Eds.), Moscow, NedraPubl. House, pp. 109-110, FIGS. 71, 72, 1974 (in Russian).

[0005] The known turbodrill comprises a housing coupled with its one endto a drill pipe for feeding drilling fluid. The housing accommodates ahydraulic motor comprising a multistage turbine, each stage of which isconstituted by a directing stator disk defining through passages and aworking rotor disk defining through passages. The rotor disk isinstalled on a shaft rotatably mounted in the housing on supports andcarries a rock breaking tool on the end thereof facing the bottomhole.The total sectional area of the stator disk through passages correspondsto the total sectional area of the rotor disk through passages. In theprocess of drilling, the rock breaking tool is brought in rotation by ahydraulic downhole motor. The flow of the drilling fluid fed through thedrill pipe changes its direction in the stator disk and in the rotordisk, and, flowing from one stage into another, gives off a part of itshydraulic power to each stage. As a result, the power generated by allthe stages is summarized on the turbodrill shaft and is transmitted tothe rock breaking tool. However, the above-described design of theturbodrill cannot provide the power and torque strength sufficient forthe normal operation of the new type rock breaking tool, unless thenumber of the downhole motor sections is increased.

BRIEF DESCRIPTIONS OF THE INVENTION

[0006] It is an object of the present invention to provide a turbodrillin which, owing to structural changes in the stator disk, a significantincrease in the power and torque strength on the rock breaking tool canbe ensured without increasing the number of the downhole motor sections.

[0007] Another object of the present invention is to make the turbodrillless metal-intensive.

[0008] One more object of the present invention is to simplify thedesign and to prolong the service life of the turbodrill.

[0009] According to the above-stated and other objects, the essence ofthe present invention is that in a turbodrill comprising a housingcoupled with its one end to a drill pipe for feeding drilling fluid, thehousing accommodating a hydraulic downhole motor which comprises amultistage turbine each stage of which is constituted by a directingstator disk defining through passages and a working rotor disk definingthrough passages, the rotor disk being installed on a shaft rotatablymounted in the housing on supports and carrying a rock breaking tool onthe end thereof facing the bottomhole, according to the invention, thetotal area of the inlet openings of the stator disk through passages isfrom about ⅕ to about ⅗ of the total area of the inlet openings of therotor disk through passages.

[0010] Such an embodiment of the stator disk provides an increase of thedrilling fluid pressure in the through passages defined by the bladesthereof. As a result, the torque strength on the rotor disk bladesincreases. For instance, with the rotor disk rotating with a speed ofabout 500 rpm and with the stator disk embodied according to the presentinvention, a torque strength of about 1800 Nm is provided on the rockbreaking tool with one-section embodiment of the downhole motor. Astator disk having the total area of the inlet openings of the throughpassages less than ⅕ of the total area of the inlet openings of therotor disk through passages will result in a substantial growth of thepressure drop on the stator disk and on the rotor disk, bringing abouthigher hydraulic losses and decreasing the turbodrill efficiency, aswell as intensive wear of the flow part of the stator disk and the rotordisk for each stage and axial support of the shaft.

[0011] An embodiment of the stator disk with the total area of the inletopenings of the through passages more than ⅗ of the total area of theinlet openings of the rotor disk through passages will result in adecrease of pressure on the stator disk, which in turn will reduce thepressure drop of the drilling fluid between the stator disk and therotor disk. This will lead to reducing the torque strength anddecreasing the power of the turbodrill, i.e., the values thereof willapproach those of the widely used well-known turbodrills.

[0012] It is preferable that the inlet openings of the through passagesof the stator disk of all the stages should lie in one diametral planeand form a through axial duct with the longitudinal axis thereofparallel to the axis of the shaft.

[0013] Such structural embodiment of the stator disk makes it possibleto feed the drilling fluid with a lower pressure drop at each stage ofthe downhole motor with the required flow-in of the drilling fluid andto provide the required torque strength for effective operation of therock breaking tool.

[0014] It is no less preferable that the inlet openings of the throughpassages of the stator disk of each stage subsequent to the incomingflow of the drilling fluid should be displaced circumferentially to theinlet openings of the stator disk of the preceding stage through atleast 1 degree, so that the outlet openings of the stator disk throughpassages of all the stages be disposed along a helical line with acenter lying on the shaft axis.

[0015] Such structural embodiment of the stator disk results in adisplacement of the drilling fluid flow and in an appearance of ahorizontal component thereof, the direction of whose vector is accordantwith the direction of rotation of the rotor disk. Thereby an additionaltorque strength is created on the rotor disk blades. For instance, withthe inlet openings of the through passages of the stator disk of eachstage subsequent to the entering flow of the drilling fluid displacedcircumferentially through 15 degrees with respect to the inlet openingsof the stator disk of the preceding stage, at least one of the outletopenings of the through passages of the of the stator disk of thepreceding stage is closed. A part of fluid acting on the blades of therotor disk enters a closed space defined by the body of the stator diskof the subsequent stage, by the walls of the through passage of therotor disk and by the walls of the through passage of the stator disk ofthe preceding stage, one of the walls being a side of the stator diskblade, and the other being the body thereof. Such a phenomenon istypical of volumetric downhole motors which are noted for enhanced powerand torque.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Other objects and advantages of the invention will become moreapparent from the following particular exemplary embodiment thereof andthe drawings, in which:

[0017]FIG. 1 shows diagrammatically a turbodrill according to theinvention, with a partially exploded view;

[0018]FIG. 2 shows a scaled-up view of the flow part assembly shown inthe exploded view;

[0019]FIG. 3 shows section A-A in FIG. 2;

[0020]FIG. 4 shows a developed view of the flow part of two stages of adownhole motor;

[0021]FIG. 5 shows a developed view of the flow part of two stages of adownhole motor, a variant of embodiment.

DETAILED DESCRIPTION OF THE INVENTION

[0022] A turbodrill according to the present invention comprises ahousing 1 (FIG. 1) coupled with one end 1 a to a drill pipe 2 forfeeding drilling fluid, the housing accommodating a hydraulic downholemotor 3 comprising a multistage turbine. Each stage is constituted by adirecting stator disk 5 defining through passages 4 (FIG. 2) and aworking rotor disk 7 defining through passages 6. The disks 7 areinstalled on a shaft 8 which is rotatably mounted in the housing 1 onsupports (not shown in the drawings) and carries a rock breaking tool 9on its end 8 a facing the bottomhole. The total area of inlet openingsof the through passages 4 of the stator disk 5 is from about ⅕ to about⅗ of the total area of inlet openings of the through passages 6 of therotor disk 7 of each stage.

[0023] Inlet openings 4 a of the through passages 4 of the stator disks5 of all the stages lie on one diameter and constitute an open axialduct 10 whose longitudinal axis 10 a is parallel to an axis 11 of theshaft 8. The proposed embodiment of the stator disk 5 makes it possibleto feed the drilling fluid with a lower pressure drop at each stage ofthe downhole motor with the required flow-in and to provide the requiredtorque strength for effective operation of the rock breaking tool 9.

[0024] The turbodrill operates in the following manner. Drilling fluidshown with dotted arrows k is fed along the drill pipe 2 to the housing1 of the turbodrill. The hydraulic energy of the fluid flow is convertedinto mechanical energy of rotation of the shaft 8 carrying the rockbreaking tool 9. The drilling fluid flow interacts with the body of thestator disk, then enters through a limited number of the inlet openings4 a into the through passages 4 restricted by blades 12, and leaves saidpassages in the form of jets. Said jets of the drilling fluid act onblades 13 of the rotor disk 7, then a part of the jet flow is directedvia the through passages 6 of the rotor in an axial direction to theinlet openings 4 a of the through passages 4 of the stator of thesubsequent stage stator, while another part of the jet flow continues tomove substantially in a horizontal direction, since it is found in aclosed space defined by the body of the stator disk 5 of the precedingand subsequent stages and by the sides of the blades 13 of the rotordisk 7. The movement of a part of the fluid jet flow in a horizontaldirection shown by arrow m promotes an increase in the torque strengthon each stage of the downhole motor, this resulting in an increase ofthe torque strength on the turbodrill shaft. The latter circumstance,with a required flow-in of the drilling fluid, causes a reduction of thenumber of the turbodrill stages when developing of the necessary torquestrength on the shaft thereof, providing effective operation of thepresent-day rock breaking tool.

[0025] A variant of the turbodrill embodiment, according to the presentinvention, is structurally similar to the above-stated, the differencebeing in the structural embodiment of the stator disk 14. In the statordisk 14 (FIG. 5) of each subsequent stage the inlet openings 15 a of thethrough passages 15 with respect to the incoming flow of drilling fluidalong arrow k are displaced circumferentially relative to the inletopenings 15 a of the stator disk 14 of the preceding stage through atleast 1 degree, so that outlet openings 15 b of the through passages 15of the stator disk 14 of all the stages are disposed along a helicalline with a center lying on the axis 11 of the shaft 8.

[0026] The turbodrill embodied as described in the above variant,operates in the following manner. Drilling fluid is fed along the drillpipe 2 to the housing 1 of the turbodrill, and the drilling fluid viathe through passages 15 of the stator disk 14, defined by the blades 12,comes to the blades 13 of the rotor disk 7. Owing to the displacement ofthe inlet openings 15 a of the stator disk in each stage there occurs acircumferential displacement of the drilling fluid flow and a horizontalcomponent thereof appears, whose vector is accordant with the directionof rotation of the rotor disk 7. Thereby an additional torque strengthis created on its blades 13.

[0027] This is due to the fact that a part of the inlet and outletopenings of the rotor of the preceding stage prove to be closed by thebody of the stator of the preceding and subsequent stages. Thus a partof the drilling fluid acting on the blades 13 of the rotor disk 7 provesto be in a closed space defined by the body of the stator disk 14 of thepreceding and subsequent stages and by the sides of the blades 13 of therotor disk 7 of the preceding stage. The fluid found in the limitedvolume interacts with the blades 13 of the rotor disk 7, creatingincreased torque strength on the shaft 8. The flow of the drilling fluidmoving from one stage to another is helix-shaped. Such character of thedrilling fluid movement is typical of volumetric downhole motors notedfor enhanced power and torque strength. For instance, circumferentialdisplacement of the inlet openings 15 a of the stator disk 14 of eachsubsequent stage in respect to the incoming flow of the drilling fluid,e.g., in the direction of rotation of the rotor disk through 15 degrees,i.e., for blade pitch of the rotor disk 7, results in closing thereof.Thereby an additional volume of fluid acting on the blades 13 of therotor disk 7 is created. This additional volume is created in the closedspace defined by the body of the stator disk 14 of the subsequent stage,by the walls of the through passage 6 of the rotor disk 7 and by thewalls of the through passage 4 of the stator disk 14 of the previousstage, one of which is a side of the blade 12 of the stator disk 14, andthe other is the body thereof. A still greater increase in the volume ofthe fluid acting on the rotor blades results in an even greater increasein the torque strength on the shaft of the turbodrill.

[0028] All the above-stated results either in increasing the torquestrength on the shaft of the turbodrill, for example, by 30% with apreset flow-in of the drilling fluid or in preserving the requiredtorque strength, e.g., of 2000 Nm, on the shaft of the turbodrill with adecreased flow-in of the drilling fluid, that allows using theturbodrill with present-day high-performance rock breaking tools.

1. A turbodrill in combination with a drill pipe comprising: a housingwhich is a bearing member and has two ends, one of said ends beingcoupled to said drill pipe; a hydraulic downhole motor arranged in saidhousing; a multistage turbine of said hydraulic downhole motor; adirecting stator disk of said multistage turbine, secured in saidhousing; supports installed in said housing; a shaft rotatably mountedin said housing on said supports, having an axis and a carrying endfacing the bottomhole; a working rotor disk of said multistage turbinedisposed on said shaft; each stage of said multistage turbineconstitututed by said directing stator disk and working rotor disk,installed sequentially downstream the drilling fluid; through passagesformed in said directing stator disk; through passages formed in saidworking rotor disk; inlet openings of said through passages in saidworking rotor disk; inlet openings of said through passages in saiddirecting stator disk, the total area of said inlet openings of saidthrough passages in said directing stator disk being from about ⅕ toabout ⅗ of the total area of said inlet openings of said throughpassages in said working rotor disk; a rock breaking tool secured onsaid carrying end of said shaft.
 2. A turbodrill according to claim 1,comprising: a diametral plane, in which there lie said inlet openings ofsaid through passages in said directing stator disk of said each stage;a through axial duct formed by said inlet openings of said throughpassages in said directing stator disk of said each stage, lying in saiddiametral plane, said duct having a longitudinal axis parallel to saidaxis of said shaft.
 3. A turbodrill according to claim 1, wherein saidinlet openings of said through passages of said directing stator disk ofsaid each stage being subsequent with respect to the incoming flow ofthe drilling fluid are displaced circumferentially through at least 1degree relative to said inlet openings of said through passages of saiddirecting stator disk of said each preceding stage, so that said outletopenings of said through passages of said directing stator disk of allthe stages of said multistage turbine are disposed along a helical linewith a center lying on said axis of said shaft.
 4. A turbodrillaccording to claim 2, wherein said inlet openings of said throughpassages of said directing stator disk of said each stage beingsubsequent with respect to the incoming flow of the drilling fluid aredisplaced circumferentially through at least 1 degree relative to saidinlet openings of said through passages of said directing stator disk ofsaid each preceding stage, so that said cutlet openings of said throughpassages of said directing stator disk of all the stages of saidmultistage turbine are disposed along a helical line with a center lyingon said axis of said shaft.